Figure 1.   Time and frequency domain presentations of event-related activity from the passive task and oddball target stimuli at Fz, Cz, and Pz. (a) Unfiltered grand average event-related potentials (ERPs). (b) Group mean event-related theta power calculated from the instantaneous power measurements in the 4-7 Hz range. (c) Group mean amplitude-frequency characteristics. Along the abscissa is the frequency in logarithmic scale, along the ordinate is the relative response amplitude in decibels. The curves are normalized such that the amplitude at 0 Hz is equal to 1 (or 20 log10 1 = 0). (d) Grand average ERPs filtered in the 4-7 Hz frequency range. Stimulus occurs at 0 ms.